(CBS/AP) HENRYVILLE, Ind. - Powerful storms leveled small towns in southern Indiana, transforming entire blocks of homes into piles of debris, tossing school buses into a home and a restaurant and causing destruction so severe it was difficult to tell what was once there. As night fell, dazed residents shuffled through town, some looking for relatives, while rescue workers searched the rubble for survivors. Without power, the only light in town came from cars that crawled down the streets.

From the Gulf Coast to the Great Lakes, the storms touched nearly all walks of life. A fire station was flattened. Roofs were ripped off schools. A prison fence was knocked down and scores of homes and businesses were destroyed. At least 16 people were killed, including nine in Indiana, and dozens of others were hurt in the second deadly tornado outbreak this week.

It wasn't immediately clear how many people were missing.

The threat of tornadoes was expected to last until late Friday for parts of Kentucky, Tennessee, Indiana and Ohio. Forecasters at the National Weather Service's Storm Prediction Center said the massive band of storms put 10 million people at high risk of dangerous weather.

"We knew this was coming. We were watching the weather like everyone else," said Clark County, Ind., Sheriff Danny Rodden. "This was the worst case scenario. There's no way you can prepare for something like this."

In Henryville, the scene was eerie and somewhat chaotic. Cell phones and landlines were not working. Hundreds of firefighters and police zipped around town. Power lines were down and cars were flipped over. People walked down the street with shopping carts full of water and food, handing it out to whoever was in need.

Terry Brishaber said his uncle's mobile home was gone.

"I don't see any remnants. I don't know where it's at," he said.

Aerial footage from a TV news helicopter flying over Henryville showed numerous wrecked houses, some with their roofs torn off and many surrounded by debris. The video shot by WLKY in Louisville, Ky., also showed a mangled school bus protruding from the side of a one-story building and dozens of overturned semis strewn around the smashed remains of a truck stop.

"I'm a storm chaser," said Susie Renner, of Henryville, "and I have never been this frightened before."

Andy Bell was guarding a demolished garage until his friend could get to the business to retrieve some valuable tools Friday night. He looked around at the devastation, pointing to what were now empty lots between a Catholic church and a Marathon station about a block away.

"There were houses from the Catholic church on the corner all the way to the Marathon station. And now it's just a pile of rubble, all the way up," he said. "It's just a great ..."

His voice trailed off, before he finished: "Wood sticks all the way up."

An Associated Press reporter in Henryville said the high school was destroyed and the second floor had been ripped off the middle school next door. Classroom chairs were scattered on the ground outside, trees were uprooted and cars had huge dents from baseball-sized hail. Authorities said school was in session when the tornado hit, but there were only minor injuries there.

Afterward, volunteers pushed shopping carts full of water and food up the street and handed it out to people. The rural town about 20 miles north of Louisville is the home of Indiana's oldest state forest and the birthplace of Kentucky Fried Chicken founder Col. Harland Sanders.

Ernie Hall, 68, weathered the tornado inside his tiny home near the high school. Hall says he saw the twister coming down the road toward his house, whipping up debris in its path.

"I knew there was some bad weather out in the Midwest that was coming this way, but you don't count on a tornado hitting here that bad," he said.

He and his wife ran into an interior room and used a mattress to block the door as the tornado struck. It destroyed his car and blew out the picture window overlooking his porch.

"There was no mistaking what it was," he said.

The threat of tornadoes was expected to last until late Friday for parts of Kentucky, Tennessee, Indiana and Ohio. Forecasters at the National Weather Service's Storm Prediction Center in Oklahoma said the massive band of storms was putting 10 million people in several states at high risk of dangerous weather.

"Maybe five times a year we issue what is kind of the highest risk level for us at the Storm Prediction Center," forecaster Corey Mead said. "This is one of those days."

CBS News severe weather consultant and chief meteorologist for CBS4 in Miami, David Bernard, explained why there are so many tornadoes so early. "We have a tremendous amount of warm air, a lot further north for so early in the season than we normally see, and then we have a powerful jet stream coming out of the Rockies, and it's splitting: One part of the jet stream going to the north, the other one going to the south, and in between that split you're get an incredible amount of air rising in the atmosphere, and that can lead to some very large storms, just like were seeing right now.

FEMA Administrator Craig Fugate issued a statement on Friday expressing condolences to those affected by the weather. He added: "In response to these latest storms, we have personnel assembled and on alert, should the affected states request additional assistance...We strongly encourage residents in impacted areas to listen carefully to instructions from their local officials and take the recommended protective measures to safeguard life and property while response efforts continue."

Cincinnati-Northern Kentucky International Airport was closed temporarily because of debris on the runways, but one of three runways had reopened by late afternoon. A fire station was flattened and several barns were toppled in northern Kentucky across the Ohio River from the badly damaged Indiana towns.

The outbreak was also causing problems in states to south, including Alabama and Tennessee where dozens of houses were damaged. It comes two days after an earlier round of storms killed 13 people in the Midwest and South.

At least 20 homes were ripped off their foundation and eight people were injured in the Chattanooga, Tenn., area after strong winds and hail lashed the area. To the east in Cleveland, Blaine Lawson and his wife Billie were watching the weather when the power went out. Just as they began to seek shelter, strong winds ripped the roof off their home. Neither was hurt.

"It just hit all at once," said Blaine Lawson, 76. "Didn't have no warning really. The roof, insulation and everything started coming down on us. It just happened so fast that I didn't know what to do. I was going to head to the closet but there was just no way. It just got us."

A home in Athens, Ala., was heavily damaged by a strong storm that swept through the area Friday, March 2, 2012. A reported tornado destroyed several houses in northern Alabama as storms threatened more twisters across the region Friday. (AP Photo/Athens News Courier, Jean Cole)(Credit: Jean Cole) Thousands of schoolchildren in several states were sent home as a precaution, and several Kentucky universities were closed. The Huntsville, Ala., mayor said students in area schools sheltered in hallways as severe weather passed in the morning.

"Most of the children were in schools so they were in the hallways so it worked out very well," said Huntsville Mayor Tommy Battle.

Five people were taken to area hospitals, and several houses were leveled.

An apparent tornado also damaged a state maximum security prison about 10 miles from Huntsville, but none of the facility's approximately 2,100 inmates escaped. Alabama Department of Corrections spokesman Brian Corbett said there were no reports of injuries, but the roof was damaged on two large prison dormitories that each hold about 250 men. Part of the perimeter fence was knocked down, but the prison was secure.

"It was reported you could see the sky through the roof of one of them," Corbett said.

For residents and emergency officials across the state, tornado precautions and cleanup are part of a sadly familiar routine. A tornado outbreak last April killed about 250 people around the state, with the worst damage in Tuscaloosa to the south.

The Storm Prediction Center's Mead said a powerful storm system was interacting with humid, unstable air that was streaming north from the Gulf of Mexico.

"The environment just becomes more unstable and provides the fuel for the thunderstorms," Mead said.

Schools sent students home early or canceled classes entirely in states including Alabama, Tennessee, Mississippi, Kentucky and Indiana. In Alabama alone, more than 20 school systems dismissed classes early Friday. The University of Kentucky, the University of Louisville and several other colleges in the state also canceled classes.

In one subdivision in in Athens, Ala., damage was visible on 10 homes. Homeowner Bill Adams watched as two men ripped shingles off the roof of a house he rents out, and he fretted about predictions that more storms would pass through.

"Hopefully they can at least get a tarp on it before it starts again," he said.

Not far away, the damage was much worse for retired high school band director Stanley Nelson. Winds peeled off his garage door and about a third of his roof, making rafters and boxes in his attic visible from the street.

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